package CryptUtil

import (
	"crypto/aes"
	"crypto/cipher"
)

var AESKey = [32]byte{
	0x13, 0x00, 0x00, 0x00,
	0x08, 0x00, 0x00, 0x00,
	0x06, 0x00, 0x00, 0x00,
	0xB4, 0x00, 0x00, 0x00,
	0x1B, 0x00, 0x00, 0x00,
	0x0F, 0x00, 0x00, 0x00,
	0x33, 0x00, 0x00, 0x00,
	0x52, 0x00, 0x00, 0x00,
}

var ivShiftKey = [...]byte{
	0xEC, 0x3F, 0x77, 0xA4, 0x45, 0xD0, 0x71, 0xBF, 0xB7, 0x98, 0x20, 0xFC, 0x4B, 0xE9, 0xB3, 0xE1,
	0x5C, 0x22, 0xF7, 0x0C, 0x44, 0x1B, 0x81, 0xBD, 0x63, 0x8D, 0xD4, 0xC3, 0xF2, 0x10, 0x19, 0xE0,
	0xFB, 0xA1, 0x6E, 0x66, 0xEA, 0xAE, 0xD6, 0xCE, 0x06, 0x18, 0x4E, 0xEB, 0x78, 0x95, 0xDB, 0xBA,
	0xB6, 0x42, 0x7A, 0x2A, 0x83, 0x0B, 0x54, 0x67, 0x6D, 0xE8, 0x65, 0xE7, 0x2F, 0x07, 0xF3, 0xAA,
	0x27, 0x7B, 0x85, 0xB0, 0x26, 0xFD, 0x8B, 0xA9, 0xFA, 0xBE, 0xA8, 0xD7, 0xCB, 0xCC, 0x92, 0xDA,
	0xF9, 0x93, 0x60, 0x2D, 0xDD, 0xD2, 0xA2, 0x9B, 0x39, 0x5F, 0x82, 0x21, 0x4C, 0x69, 0xF8, 0x31,
	0x87, 0xEE, 0x8E, 0xAD, 0x8C, 0x6A, 0xBC, 0xB5, 0x6B, 0x59, 0x13, 0xF1, 0x04, 0x00, 0xF6, 0x5A,
	0x35, 0x79, 0x48, 0x8F, 0x15, 0xCD, 0x97, 0x57, 0x12, 0x3E, 0x37, 0xFF, 0x9D, 0x4F, 0x51, 0xF5,
	0xA3, 0x70, 0xBB, 0x14, 0x75, 0xC2, 0xB8, 0x72, 0xC0, 0xED, 0x7D, 0x68, 0xC9, 0x2E, 0x0D, 0x62,
	0x46, 0x17, 0x11, 0x4D, 0x6C, 0xC4, 0x7E, 0x53, 0xC1, 0x25, 0xC7, 0x9A, 0x1C, 0x88, 0x58, 0x2C,
	0x89, 0xDC, 0x02, 0x64, 0x40, 0x01, 0x5D, 0x38, 0xA5, 0xE2, 0xAF, 0x55, 0xD5, 0xEF, 0x1A, 0x7C,
	0xA7, 0x5B, 0xA6, 0x6F, 0x86, 0x9F, 0x73, 0xE6, 0x0A, 0xDE, 0x2B, 0x99, 0x4A, 0x47, 0x9C, 0xDF,
	0x09, 0x76, 0x9E, 0x30, 0x0E, 0xE4, 0xB2, 0x94, 0xA0, 0x3B, 0x34, 0x1D, 0x28, 0x0F, 0x36, 0xE3,
	0x23, 0xB4, 0x03, 0xD8, 0x90, 0xC8, 0x3C, 0xFE, 0x5E, 0x32, 0x24, 0x50, 0x1F, 0x3A, 0x43, 0x8A,
	0x96, 0x41, 0x74, 0xAC, 0x52, 0x33, 0xF0, 0xD9, 0x29, 0x80, 0xB1, 0x16, 0xD3, 0xAB, 0x91, 0xB9,
	0x84, 0x7F, 0x61, 0x1E, 0xCF, 0xC5, 0xD1, 0x56, 0x3D, 0xCA, 0xF4, 0x05, 0xC6, 0xE5, 0x08, 0x49}

type AESOFB struct {
	mapleVersion uint16
	iv           []byte
	key          *[32]byte
	aes          bool
}

func NewMapleAESOFB(key *[32]byte, iv []byte, mapleVersion uint16, aes bool) *AESOFB {
	return &AESOFB{encodeMapleVersion(mapleVersion), iv, key, aes}
}

func encodeMapleVersion(mapleVersion uint16) (res uint16) {
	res = (mapleVersion >> 8 & 0xFF) | (mapleVersion << 8 & 0xFF00)
	return
}

func GetPacketLength(header []byte) int {
	if len(header) < 4 {
		return -1
	}
	return int((uint16(header[0]^header[2]) & 0xFF) | ((uint16(header[1]^header[3]) << 8) & 0xFF00))
}

func (this *AESOFB) GetPacketHeader(len uint16) []byte {
	iiv := ((uint16(this.iv[3])) | ((uint16(this.iv[2]) << 8) & 0xFF00)) ^ this.mapleVersion
	mlength := (((len << 8) & 0xFF00) | (len >> 8)) ^ iiv
	p := make([]byte, 4)

	p[0] = byte((iiv >> 8) & 0xFF)
	p[1] = byte(iiv & 0xFF)
	p[2] = byte((mlength >> 8) & 0xFF)
	p[3] = byte(mlength & 0xFF)
	return p
}

func (this *AESOFB) Crypt(buf []byte) {
	if this.aes {
		this.AesCrypt(buf)
	} else {
		this.SubCrypt(buf)
	}
}

func (this *AESOFB) AesCrypt(buf []byte) {
	remaining := len(buf)
	llength := 0x5B0
	start := 0
	myIv := make([]byte, 16)
	for i := 0; i < 4; i++ {
		copy(myIv[4*i:], this.iv[:])
	}
	for remaining > 0 {
		if remaining < llength {
			llength = remaining
		}

		block, err := aes.NewCipher(this.key[:])
		if err != nil {
			return
		}
		stream := cipher.NewOFB(block, myIv)
		stream.XORKeyStream(buf[start:start+llength], buf[start:start+llength])

		start += llength
		remaining -= llength
		llength = 0x5B4
	}
	this.updateIv()
}

func (this *AESOFB) SubCrypt(buf []byte) {
	b := this.iv[0]
	for i, l := 0, len(buf); i < l; i++ {
		buf[i] += b
	}
	this.updateIv()
}

func (this *AESOFB) updateIv() {
	newiv := [4]byte{0xF2, 0x53, 0x50, 0xC6}
	var input, valueinput byte
	var fulliv, shift uint32

	for i := byte(0); i < 4; i++ {
		input = this.iv[i]
		valueinput = ivShiftKey[input]

		newiv[0] += ivShiftKey[newiv[1]] - input
		newiv[1] -= newiv[2] ^ valueinput
		newiv[2] ^= ivShiftKey[newiv[3]] + input
		newiv[3] -= newiv[0] - valueinput

		fulliv = uint32(newiv[3])<<24 | uint32(newiv[2])<<16 |
			uint32(newiv[1])<<8 | uint32(newiv[0])
		shift = fulliv>>0x1D | fulliv<<0x03

		newiv[0] = byte(shift & uint32(0xFF))
		newiv[1] = byte(shift >> 8 & uint32(0xFF))
		newiv[2] = byte(shift >> 16 & uint32(0xFF))
		newiv[3] = byte(shift >> 24 & uint32(0xFF))
	}

	copy(this.iv[:], newiv[:])
}

func (this *AESOFB) CheckPacket(packet []byte) bool {
	return ((uint16(packet[0]^this.iv[2]) & 0xFF) == ((this.mapleVersion >> 8) & 0xFF)) && ((uint16(packet[1]^this.iv[3]) & 0xFF) == (this.mapleVersion & 0xFF))
}
